You may lose lots of pedal as you increase the volume of fluid needed for master to fill cylinders. That's why you have a 1-1/4" bore on your master  and it is four times the length of one wheel  cylinders stroke plus a little . 1-3/8 will give you great stopping ,but it may not be until second pump . Just a thought .
  The turn around on my rebuild was less 2 weeks with shipping . You can let one leak or take it off , cap it ,and use on three. While sending  four back if your spares are same .

Hagen Hwy, cost me 55 ea. last year in stainless and include total rebuild . He went above and beyond by replacing the stripped bleeders with flesh edged old stock that matched my patina and a bad piston  . Just under 500 for 4 cylinders and all brake shoes relined with new proper soft linings ,bonded for longer life . Go Original . And shipped to Pa.

Yes , be careful most new cylinders are step type . They would have to be changed in pairs and will use a little more fluid ,hence may lower pedal .  You talk about a firm pedal is it braking good . Found you'll get hard pedal as hoses collapse and prevent fluid return . I say sleeve also  Hagens Hwy  Auto does great work .

Had similar problem this year . was coarse rust in tank restricting fuel flow . But not making to fuel filter to show up. Top of tank was rotting away ,more I drove worst it got .